A turbomachine is generally equipped with temperature sensors, for example thermocouples that are used for measuring high temperatures, or resistive probes that provide information about the temperature of the flux that passes through the turbomachine in various transverse planes of the turbomachine. In this document, the term “transverse plane” describes a plane that is perpendicular to the reference axis of the turbomachine. These temperature measurements must be extremely reliable.
Therefore, in order to make certain that the temperature measured is truly representative of the temperature of the flux in a given transverse plane of the turbomachine, two thermocouples are usually placed in each transverse plane of the turbomachine for which it is necessary to measure the temperature of the flux. Since the temperature of the flux is relatively homogeneous in the same transverse plane upstream of the combustion chamber, these two thermocouples are generally placed in the same location of the transverse plane, but downstream of the combustion chamber, as the temperature of the flux is non-homogeneous in the same transverse plane, the two thermocouples are generally placed in two different locations in the same transverse plane.
Besides this redundancy of sensors in each transverse plane, it is also essential to ensure that each of the thermocouples is not defective. This verification of the temperature sensors is simple for those that are placed upstream of the combustion chamber, since all that needs to be done is compare the temperatures measured by the two thermocouples—when the sensors are thermocouples, as is the case for exemplary purposes in the rest of this description—that are located in the same transverse plane. In fact, since these thermocouples are positioned in the same location of the transverse plane, if they are functioning correctly exactly the same temperature should be measured with both thermocouples. Conversely, if a discrepancy in the temperatures of these two thermocouples is detected, it may be deduced that one of the two thermocouples is defective.
However, such a method for monitoring the thermocouples cannot be carried out so effectively downstream of the combustion chamber, and particularly at the inlet to the low pressure turbine, because the two thermocouples in this zone are not located in at the same site of a common transverse plane, they are offset with respect to one another within the transverse plane. Accordingly, downstream of the combustion chamber the flux exhibits large thermal disparities, with the result that the temperatures measured by each sensor are different, even when the thermocouples are functioning properly. Consequently, it is no longer possible to anticipate or detect a malfunction of one of the thermocouples with the method described in the preceding, or if such a malfunction should be detected it would be with considerably delayed.